1. Field of the Invention
This invention relates generally to safety control systems and more specifically to an ignition safety control system for preventing energization of electrical components within an engine compartment until the compartment has been sufficiently ventilated of flammable vapors.
2. Description of the Prior Art
Substantially enclosed compartments housing internal combustion engines are particularly susceptible to dangerous explosions resulting from ignition, by electrical components of the engines, of combustible vapors trapped therein. The above problem is particularly acute in vehicles such as power boats where the engine compartments may remain closed for prolonged periods of time enabling highly volatile fuels such as gasoline or diesel fuel within the chamber --whether from the carburetor, leaks in fuel lines or the like --to vaporize and become entrapped within the compartment in dangerously explosive concentrations. Sparks from the starter motors brushes, the ignition coil or the distributor which are normally produced in the subsequent starting or running of an engine within the compartment may cause the entrapped vapors to ignite resulting in an explosion and fire that can severely damage or destroy the entire boat and cause serious injury to individuals thereon.
Boat manufacturers, recognizing the above problem, have typically provided the boat engine compartment with a ventilating apparatus including a blower in fluid communication with the engine compartment for exhausting the explosive vapors therefrom. The foregoing problem has also been specifically recognized in regulations promogated by the United States Coast Guard which require a definite period for clearing vapors from the engine compartment to elapse, before the engine can be operated. As a result, various ignition lockout devices have been designed for use specifically with the ignition systems of power boats.
The conventional ventilation blower for the engine compartment is generally operated by a manual switch on the control console of the boat, and does not inhibit the ignition switch of the engine. Modifications of the basic blower have included vapor detectors located within the compartment or time delay elements for providing visual or audible warnings to the boat operator indicating the explosive condition of the compartment. With the basic blower systems, however, the boat operator was entirely free to disregard the warnings and to start the engine before the blower had been operated a sufficient length of time to insure proper ventilation of the engine compartment.
Various ignition safety lockout devices have appeared in the prior art which include combinations of the vapor detector and visual or audible operator warning safety features. These safety ignition lockout devices typically operate in response to a movement of the ignition switch for starting an engine within the engine compartment from its OFF to its ON position. Various configurations have been introduced to either physically prevent the operator from advancing the ignition switch to its START position or to electrically disable energization of the engine's starter motor until the engine compartment had been properly ventilated.
A first group of the prior art ignition lockout devices have ignition disabling apparatus controlled by a vapor detector within the engine compartment. Such devices depend for their reliability upon the accuracy, the proper functioning and proper location of the vapor detector within the engine compartment. Further, rugged environmental conditions to which such gas detectors are typically exposed in such systems render their use undesirable from a reliability standpoint.
A second group of prior art ignition safety lockout devices include apparatus for establishing a time delay period during which the starter motor of the engine is disabled simultaneously with the activation of an exhaust blower within the compartment. Such devices have typically employed temperature responsive elements such as bimetallic strip configurations or time delay relays for establishing the desired time delay. The repetitive timing accuracy of such elements obviously depends in part upon the ambient temperature and upon the frequency at which these devices are energized. Further, the reliability of such electromechanical devices depends upon the particular construction and wear of the electromechanical parts.
Most prior art ignition safety lockout systems are further designed to deenergize the exhaust blower prior to or simultaneously with the starting of the engine. Such systems do not provide for removal of explosive vapors which may accumulate within the engine compartment during the starting sequence of the engine, but rely upon the exhausting capabilities of the engine itself to clear such vapors from the compartment when the engine is running.
One prior art system includes relay apparatus for maintaining the blower in an energized state for a predetermined time period following any attempt to start the engines within the engine compartment. The continued blower activation, however, requires that the ignition switch be maintained in an ON position. Further, while this system provides for enabling of the blower, it does not sense whether or not the blower has actually been energized as assumed.
The prior art ignition safety lockout devices do not detect the successful starting of enabled engines after the initial exhaust expulsion time delay period, nor do they sense the operative state of the engines thereafter. Their operation, therefore, is generally not dependent upon the operative state of the engines being controlled. If an attempted restart of the engine is tried after the ignition key has been turned to its OFF position, most prior art systems require a complete recycling for an additional predetermined time delay period regardless of the time interval between successive engine start attempts.
The disadvantages of the prior art ignition safety control devices are overcome by the novel ignition safety control system of the present invention. The ignition safety control system of the present invention senses the operative state of both blower(s) and engine(s) within the engine compartment and automatically enables the energization thereof based upon the occurrence of logical sequences of predetermined events and time periods.
Besides providing for proper initial engine compartment ventilation, the system of the present invention enables repetitive attempts to start the engine(s) without system recycling after the ignition switch has been turned to its OFF position and provides for post start blower activation control based upon the operative status of the engine(s).
While the present invention will be described in conjunction with its use in a power boat, it will be understood that the invention is not limited to this use, but is applicable for use in the ignition system of any internal combustion engine housed in an engine compartment susceptible of accumulating explosive vapors.
Further, while the present invention is described with reference to specific embodiments of switching, timing, and other logic circuitry, it will be understood that the invention is not limited to the use of the specific circuits of the preferred embodiment, but, that any equivalent circuits may be used which perform the same functions without departing from the spirit or intent of this invention.